Jack-knifing is a serious problem for tractor-trailer combinations, and existing systems for solving the problem have not been successful.
Several prior art patents have addressed towing problems. U.S. Pat. No. 1,372,677 (Dellett et al.) describes a tractor steering hitch for farm use wherein a slidable hitch is used on a trailer to cause its wheels to follow in the tracks of the tractor in passing around curves. While this is of some help in forcing a trailer to follow a tractor, the trailer does not move transversely of the tractor until the angle between the tractor and trailer changes. Turning the front wheels of the tractor while the combination is stationary has no effect on the position of the trailer. In U.S. Pat. No. 3,063,739 (Davies) a fifth wheel plate is fixed to a tractor chassis on its center line. The device incorporates two vertical axes spaced rearwardly from one another on the longitudinal axis of the trailer, and the fifth wheel plate is locked to, and swings about, either of these axes. There is no horizontal movement of the fifth wheel plate or the hitch means.
Systems shown in U.S. Pat. No. 2,922,660 (Haugland et al.), U.S. Pat. No. 4,153,132 (Biedebach) and U.S. Pat. No. 4,212,483 (Howard) consider improvements in connections between the tractor and the trailer, but none of these systems would efficiently compensate for the forces which cause skidding or jack-knifing.
U.S. Pat. No. 4,204,700 (Haines) shows an anti-jackknife apparatus which is hydraulically controlled but which merely limits the turning angle of the trailer to cause it to follow the tractor. U.S. Pat. No. 4,313,615 (Simon) describes a system in which a steering mechanism is connected to a pivotable disk which controls hydraulic cylinders placed between a forward member and a rearward member of an articulated vehicle so that angular movement of the rearward member is severely limited. U.S. Pat. No. 2,461,212 (Hanna) concerns maintaining the alignment of a tractor and a trailer. An arrangement is provided for allowing the trailer to turn with respect to the tractor only when the tractor is intentionally turning a corner.